Scalable Encryption Algorithm (SEA) is a parametric block cipher for resource constrained systems (e.g., sensor networks, RFIDs). It was initially designed as a low-cost encryption/authentication routine (i.e., with small code size and memory) targeted for processors with a limited instruction set (i.e., AND, OR, XOR gates, word rotation, and modular addition). Additionally and contrary to most recent block ciphers (e.g., the DES and AES Rijndael), the algorithm takes the plaintext, key, and the bus sizes as parameters and, therefore, can be straightforwardly adapted to various implementation contexts and/or security requirements.